This invention relates to a vehicle wheel with an internally located emergency wheel and more particularly to emergency wheels that are cheaper and easier to manufacture and that provide greater stability when in use than is the case in the previously known emergency wheels.
Emergency wheels are known. See for instance German Utility Model No. 1,950,530. Such a wheel includes a gas-filled tubeless rubber tire mounted on a well-based (deep channelled) rim with an annular emergency wheel composed of segments, the segments being clamped on the rim by means of screws radially penetrating the rim, the segments of which are further constructed from cast light metal which is substantially double T-shaped in cross-section with a narrow segment foot located radially adjacent the well center of the rim and with a wide segment head stiffened by radial ribs. The radially inner region of each of the respective segments is narrower axially by at least half the tire bead width than the clear interval between the tire beads. In spite of the relatively narrow configuration thereof, the segment foot is braced against the inner edges of the tire beads through the use of clamp springs which are constructed in the manner of spreading springs that spread themselves between the tire beads by cooperation with wedge surfaces of the segments when the segments are tightened radially. By this means, the segments are intended to be stabilized between the lateral beads of the tire and aligned in a precise position at right angles to the axis in case the emergency wheel must come into use. Additionally, the tire bead is intended to be retained in secure axial contact with the clinch by the spreading springs after the pressure of the tire is relaxed.
This emergency wheel has various disadvantages; principally, the assembly is highly complicated because the segment fitted with the spreading springs cannot immediately be drawn in radially between the tire beads. It may be noted that the clear interval of the tire beads in the pressureless state of the tire, such as would exist during the assembly of the emergency wheel, is smaller than the axial interval of the two ends of the spreading springs in the relaxed state. It would therefore be necessary, in order to assemble this emergency wheel, to stick the tire beads to the clinches. This is only possible when the tire is inflated, for which purpose the screw passage holes would have to be sealed prior to inflation in the case of segments located loosely inside the tire, which is likewise highly complicated. The sealing between the fastening screw of the segment, which must be introduced subsequently, and the rim is effected on the introduction side of the screw in the form of a sealing washer placed beneath the screw head, which facilitates the assembly. However, if a yielding sealing washer is used, this causes the clamping force of the fastening screw to be inadmissibly restricted. In an emergency the fastening screws of the emergency wheel are stressed to the same degree as the wheel fastening screws. However, a non-yielding sealing washer using an inserted soft-sealing ring which must be used in such emergency wheels to prevent leakage would inevitably have large dimensions, both in diameter and also in the axial direction, so it would no longer be possible to accommodate such a sealing washer in the narrow remaining radial gap between the inside of the rim and the brake drum. The sealing between screw and rim should therefore be effected on the contact side of the segments for space considerations, however, this again raises assembly problems. Another disadvantage of this emergency wheel from the assembly standpoint is the absence of any possibility of maneuvering the segments into the correct circumferential position; it must be remembered that all the segments which together form a full ring are at first arranged loosely inside the tire and spread themselves about the tire where their random relative circumferential position is not detactable. The required sliding distances of the segments into a correct circumferential position are also relatively great. All this renders the assembly of the known emergency wheels so complicated and so time-consuming that practical manufacturing operations have hitherto, except for compelling exceptions, resisted any introduction of emergency wheels.
An object of this invention is to eliminate these above-noted and other disadvantages and to improve the emergency wheel configuration so that it can be assembled easily and with an acceptable time outlay.
This object is achieved according to the invention by providing an emergency wheel in which the radially inner region of each segment and the tire beads define between them a space. The emergency wheel according to preferred embodiments of the invention includes two clamp screws for cooperative engagement with each segment communicating with the segment through passage holes provided in the rim. The passage holes are uniformly spaced around the circumference of the rim, sealing means for providing an airtight seal between the rim and clamp screws on the segment contact side of the rim are provided which include a loop-ring seal formed of rubber elastic material and are positioned in a radially outwardly, relative to the wheel, conical countersink of the segment. The countersink has a relief for retaining the loop-ring such that it overlaps radially inwardly.
Also in preferred embodiments of the wheel of the present invention it is provided that the inside of each segment foot has on its entire circumference outside the region of the screwthreaded bore, axially oriented grooves the mutual interval of which is equal to or less than the diameter of the passage holes.
Since the space between tire bead and segment foot in the present invention is kept totally free of installations, and particularly contains no spreading springs as in known safety wheel configurations, not only is the highly complicated sticking of the tire beads to the clinches made superfluous, but the segments can also be displaced in the circumferential direction without great resistance even in the relaxed state of the tire. At least the segment located respectively at the top can readily abut the rim with its segment foot sole. The necessary sliding distance for a circumferentially correct adjustment of the segments is greatly reduced by the double screwing of each segment and the uniform screw pitch. In the case of four segments, the maximum displacement correction for each segment in the least favorable case is 22.5.degree..
By virtue of the relief in the region of the countersunk section accommodating the sealing ring, the latter can be inserted easily and retained securely therein, so that no assembly problems whatsoever arise in this respect. The axial grooves permit a reliable levering onward of the segments in the circumferential direction with a screwdriver though one of the screw passage holes. Particulrly, the one-sided bevelling of the groove flanks permits a positive mechanical detection of the circumferential direction in which the segment can be levered on by the shortest route to a suitable circumferential position. The overall assembly time can be reduced to approximately 10 minutes by the measures according to the invention; that is to say, the assembly of a tire including the emergency wheel according to the invention takes an experienced operator only approximately 5 minutes longer than a plain tire assembly of the same size.
The axial clearance on both sides between the segments and the tire beads also permits, in the case of an emergency run, an axial lifting of the tire beads from the clinches and shoulders of the rim, so that the slip between wheel and tire which occurs during emergency running occurs at this relatively lightly stressed point, but not in the region of the highly-stressed contact between emergency wheel and inside of the wheel tire. The rubber wear is consequently much less, which produces quieter running of the emergency wheel and a longer distance which can be covered in an emergency. The increase in the number of screw positions also stabilizes the individual segments radially and axially irrespective of the rim clinches and/or of the tire beads, so that quiet emergency running can be ensured even in the case of a lateral stressing of the emergency wheel.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention.